By Steve Schifferes BBC News Online Washington correspondent

An influential think-tank has urged the Bush administration, and the United Nations, to begin planning now for a transitional administration to govern a "post-conflict" Iraq.

Frederick Barton, a former UN deputy high commissioner for refugees, told a conference at the Centre for Strategic and International Studies in Washington that "winning the peace" was just as important as winning the war.

Neither running a war nor organising the peace can be done in haste or on the cheap Frederick Barton, Centre for Strategic and International Studies

But he warned that "military deployments to the Gulf have not been matched by visible, concrete actions by the US, the UN, or others to prepare civilian resources and personnel to handle the immense reconstruction challenges that post-conflict Iraq will face."

And he said that, if concrete resources were not devoted now to the task of civilian reconstruction, it would make it more likely that US military forces would be left in sole effective charge of running Iraq for some time to come - which appears to be the current administration plan.

Civilian set-up

Mr Barton said that the lessons of previous UN transition regimes, such as Afghanistan, Kosovo, and East Timor, demonstrated that early planning and commitment of resources is vital to ensure a successful transition to democracy.

A new post-Saddam administration would need to be created

He called for the UN Security Council to establish a transitional administrator - or at least coordinator - now to begin planning the creation of a civilian regime in Iraq.

A multi-national civilian administration "would avoid pitfalls attached to military occupation and the absence of broadly acceptable Iraqi opposition leaders, while carrying with it the legitimacy of international approval," he said.

Mr Barton argues that Iraq is not a "failed state" like Afghanistan or Kosovo, as it has a centralised government and functioning bureaucracy. He believes that it will be necessary to use elements of the existing bureaucracy, purged of their pro-Saddam elements, to keep the country running.

And the report argues for a special coordinator for national dialogue - an Iraqi - to organise consultation on the return to democracy, drafting a new constitution, and agreeing a procedure for dealing with past wrongs, such as a truth and justice commission.

Police and money

One of the most important lessons of past transitions is the need to put into place rapidly an international police force to maintain security, Mr Barton says.

Reconstruction in Kosovo was slow, and security weak

He suggests that up to 15,000 soldiers and others drawn from Europe as well as the US, should be trained to play a policing role in post-conflict Iraq and readied to be deployed as soon as the war is over.

Their role will be even more important because of the likelihood of revenge attacks by ethnic groups like the Kurds and Shia against former members of the regime.

And they could also play a role in ensuring that humanitarian aid reaches war refugees.

Oil debts

The report points out that there will be huge costs attached to rebuilding Iraq which will arise before any oil revenues come on stream to help defray the costs.

These could amount to between $25bn and $100bn, including the rebuilding of ports, roads, electricity supply, and the oil fields.

The report calls for the convening of an international donor conference, including the IMF and the World Bank, to begin planning for these reconstruction needs.

And, it says, the West and the Gulf Arab states and Saudi Arabia will have to forgive the huge debts which Iraq owes them, estimated at a crippling $383bn - more than 15 times Iraq's GDP.

More than half of these are compensation claims from Kuwait and Saudi Arabia relating to damages during the last Gulf War, only a fraction of which have been paid.

But Iraq also owes Western governments and banks around $90bn, and has another $57bn in contractual obligations to foreign firms, especially Russian and French companies involved in oil exploration.

Mr Barton says that much of this will have to be forgiven or written off through international negotiation in order to free Iraq's oil revenues for use in reconstruction.

Rebuilding Iraq will be the biggest challenge the international community has yet faced.

But, says Mr Barton, "neither running a war nor organising the peace can be done in haste or on the cheap".